This invention relates to a storage system for operating a database, in particular, a reorganization method of a database.
Conventionally, a database management system (DBMS) for managing a database is designed to increase database responsiveness. A storage area of a storage system or the like is designed such that a storage area of a database is not changed frequently, so as to avoid complex management as much as possible. Therefore, in the storage area of a database, “fragment” is gradually caused with the elapse of operating time. The term “fragment” means generation of a fragmented space, an uncollected area, or imbalance in a space management structure. The fragment in the storage area degrades database responsiveness (I/O performance or search performance) leading to an inducement for unexpected use of the storage area.
In order to eliminate the fragment in the storage area, DBMS is generally provided with dedicated software. The software eliminates the fragmentation, collects the uncollected area, and balances the space management structure on the storage area of the database, so as to change the storage area into an ideal state without any fragment. This processing is called “reorganization”.
An administrator of the DBMS is required to regularly implement the reorganization using reorganization software so as to eliminate the degradation of database responsiveness and the unexpected use of the storage area.
As regards such reorganization, there has been known a storage system, for example, in which data in a reorganization source is transferred to a reorganization destination storage system so as to reorganize a database in the reorganization destination. After the data has been reorganized in the reorganization destination, update occurred in the reorganization source during the reorganization is applied to the reorganization destination so as to switch the data to be used by the DBMS to the reorganization destination (for example, “Online database reorganization function”, issued by Hitachi Ltd., searched on Apr. 10, 2005, on the Internet, which can be located with the listing hitachi.co.jp/Prod/comp/soft1/4vsp/products/dbr.html>).
Moreover, the amount of data has been increasing in databases in recent years. Accordingly, the reorganization of all data needs a long processing time. Therefore, there has been known a storage system in which reorganization is implemented only for the data in a storage area designated by an administrator or the like (for example, “IBS Parallel Reorganization”, issued by IBM, searched on Apr. 10, 2005, on the Internet under the listing of 6.ibm.com/jp/domino02/NewAIS/aisextr.nsf/ByLetterNO/DBA04099?OpenDocument&ExpandSection=1>). In other words, data is divided to be stored into a plurality of storage areas, and only the data in a storage area designated by an administrator or the like is reorganized.